The Eye

The eye is the human's most important sensory organ. Over 90% of all sensory perception takes place through our eyes. Even though, the eye is one of the smallest organs. It has an approximate global shape, on average 23,5 mm long and only a few grams in weight.

The eye is held in place by elastic ligaments and fat cushioning and is able to move with the help of six different muscles, which compromise, in relation to their size, the fastest and strongest of the body.

Together the cornea and lens are the optical apparatus of the eye, comparable to the lens of a camera. From the total refraction, which amounts to 57-60 dpt (dpt=Dioptre) in a normal eye, the cornea, with 43-45 dpt, has the largest percentage of refraction. The cornea is approx. 0,5mm thick and has a diameter of 11-12mm.It is normally transparent, very resilient and elastic.

The lens, which sits behind the pupil and is fastened with fine filaments to a circular muscle, controls the rest of the refraction. By activating this muscle (ciliary muscle), the refraction of the lens can be increased and subsequently, objects that are closer can be seen focused(accomodation). This increase of refraction can be compared to the focusing of a camera. The ability to focus on close objects decreases with age, so that approx. with 45 years, most people need glasses.

The retina acts like the film in a camera. Light-sensitive cells, which are separated in those which sense red, green and blue, as well as black-white light, act as receptors and process the image somewhat and then transport it via the optic nerve to the brain. The setting of intensity and contrast is already taken care of, for the most part, by the retina.

The brain's performance in the processing of the image is quite substantial. Selective perception, 3-dimensional vision, movement vision, and form recognition and much more are completely due to "brain power". This performance is not necessarily hereditary, but rather is trained within the first 5 years of life. If this training happened to be incomplete, the result is a weakness in vision (Amblyopia), that doesn't involve the eye itself. This is often the case with cross-eyedness (strabismus) and extreme astigmatism.